The relationship between the rim and the tone ring is very important, and it’s difficult to separate the two because they act together as a unit.
The simplest pot design is one with no tone ring at all, just a beveled top edge, as in a drum. These are also the lightest weight ones, normally.
The next step in sophistication would be to add a brass ring at the top which the head crosses over - this adds a little weight and changes the sound. Banjos have been made like this for more than a hundred years - sometimes with a thin spun skirt. The Vega “Little Wonder” is one example. Here’s an old rim with a ring and spun skirt - this has a one-piece steamed rim with a scarf joint, and the rim is barely 3/8” thick:
This would make a great - sounding banjo for old-time music, I think. The tone ring is balanced with the rim and it’s simple.
History - sorry.
In the “golden age” of banjo design in the early 1900s, everyone was trying to come up with a better design than the next guy - there was a lot of innovation, and manufacturers respected each other’s designs and tried not to copy each other.
Gibson and Vega were two particularly innovative companies, and strong competitors, I think.
Gibson came up with the idea of using a tube rather than a solid hoop, and in order to let it ring, they elevated it above the rim with ball-bearings:
This was then developed into a much more elaborate design, where a bigger ring was supported by ball bearings pushed upwards by springs - possibly the most elaborate banjo construction ever done - It was called the “Mastertone”.
In order to accomodate the holes and springs, a very wide rim was needed. The maple rims made during this period were especially well-made, and, unfortunately, this high level of rim building crafsmanship did not continue into the 30s.
Vega felt that this design was an infringement on their newly popular “Tu-Ba-Phone” design, and they challenged Gibson, who acquiesced and abandoned the hollow tube design and invented the cast bronze tone ring - the “arch top”, which was a take off of the Ball bearing design, although much simpler - this led to the 3/4” rim, required by 3/4” tone rings which had to sit on the rim.
Once you cast something in bronze, you are stuck with it - it is “cast in bronze” - like "carved in stone", so from this point forward into eternity, ALL Gibson banjos had to have the tone ring be 3/4” wide - the tension hoops, with their 4-string string space, and flanges were dependent on that. Gibson became the “cast in bronze” company, although that did not hurt them, because Earl Scruggs bought one, and the rest is history.
Vega continued to fabricate everything, which gave them a little more flexibility, but at the cost of efficiency. - Vegas were all over the map - 11”, 10 15/16” , 10 7/8" rims, you name it. Every Vega is a “custom model”- not a bad thing at all. - They are great banjos with a soul born of handcraft. They had a special design for everyone (just like I do ha ha)
Other companies made spun-brass parts- Here’s a Bacon “Silver Bell model with a spun tone ring:
It was the era of great innovation in banjo design.
I have to point out that all this investment in banjo development was NOT done to attract 5-string banjo players - Most 5 string banjo players couldn’t afford these snazzy instruments - it was because of jazz and popular bands. 5 string banjo players benefited from the fact that these companies were trying to sell banjos to professional jazz players. The date of Earl Scruggs’ birth, 1924, was also the first 5-string banjo EVER made by Gibson.
In terms of the project, generally speaking, banjos used for bluegrass are heavier than those used for clawhammer and old time music. The model I have described, established by Gibson in the late 1920s is a heavy wood rim with a heavy cast copper alloy tone ring which sits flat on the top of the wooden rim.
Here is a photo of various tone rings and their respective weights:
Here is a drawing (in scale) of a 1927 Gibson and a 1925 Vega Tu-Ba-Phone.
These are in scale!! you can see how much more massive the Gibson model is compared to the Vega model.
NONETHELESS - I repeat - nonetheless, the Tu-Ba Phone is just as loud as the Mastertone, even without the resonator ( I have sound files, but cannot figure out how to attach them on this post) I'll do it later if anyone is interested
Later ones had the rim thickness at the bottom reduced because of the ”one piece” flange, which served the same purpose as the 49-piece assembly of the Vega bracket band - you can see how Gibson was using “value engineering” to refine their products.
Here is a drawing of the later Mastertone and several later Vega.
NOTE how the Vega rims are cut back to cantilever the tone ring - This is an important element I want to explore in this project.
SO this brings me to my own designs, which are the subject of this long thread. I am not casting, spinning, or fabricating (in the Vega mold).
My tone rings are brazed together, and the brazing creates stresses that I think enhance the sound.
My rims are 5/8” - which seem to me to be balanced with the weight of my tone rings
I am trying to find a nice relationship between the tone ring and the rim, and do something that hasn’t been done before - EVERYTHING has been done before, but I’m doing my best -We’ll see how it goes.